Ulnar nerve innervation of the triceps muscle: real or apparent? An anatomic study

A Tardy Ulnar Palsy with an Anomalous Course of Ulnar Nerve

Variations are inherent feature of the intricate brachial plexus. They can be at the level of origin, the course, or the innervation pattern of each peripheral nerve. Knowledge of the various described variations can be worthwhile during the routine hand surgery procedures. We present a case of an elderly patient with anomalous intramuscular course of the ulnar nerve presenting with ulnar neuropathy at the elbow. Level of Evidence:  IV.

Anatomic and histomorphometric study of the nerve to the vastus lateralis in cadaver for its clinical application in facial reanimation

BACKGROUND

The innervated vastus lateralis flap (IVLF) is a barely used possibility for facial palsy reconstruction because of its thickness compared to the gracilis, latissimus dorsi, and pectoralis minor flaps. The aim of this study is to perform a precise description of the intramuscular distribution of the nerve motor branches and its relationship with the vascular pedicle in order to harvest a segmental muscle flap with the best contractile strength to restore facial reanimation.

METHODS

The study was performed on 16 adult cadaver thighs identifying the vastus lateralis muscle and the distribution and relationships of its neurovascular pedicle and branches. We evaluated where the nerve pierced the muscle and the course of the nerve within it. Transverse segments of the nerve were obtained from the proximal and distal ends of the nerve and stained using anti-ChAT (Choline acetyltransferase) antibodies which are specific of motor neurons.

RESULTS

A nerve for the vastus lateralis from the posterior division of the femoral nerve divided into 2 branches in 56% of cases; the principal branch coursed along the vascular pedicle and pierced the muscle more proximally than the respective vessels, and a minor branch that pierced the muscle 25-60 mm proximally. There were 3 main intramuscular branches. The nerve length (mean 132.65 ± 22.89 mm) allowed to reach the contralateral side of the face in almost all cases (95%). The mean ChAT positive fibers was 351.0 ± 92.4/mm² at the proximal end, and 270.3 ± 87.9/mm² at the distal end (p = 0.49). The number of ChAT negative fibers was higher than ChAT positive in both proximal and distal ends of the nerve.

CONCLUSION

We propose the IVLF as a one-step surgical flap for facial paralysis reanimation due to the constant neurovascular pattern and lengthy pedicle. The amount of motor fibers in several segments of the nerve is appropriate to produce a powerful contraction for dynamic reconstruction.

Triceps and cutaneous radial nerve branches investigated via an axillary anterior arm approach: new findings in a fresh-cadaver anatomical study

OBJECTIVE

The authors sought to describe the anatomy of the radial nerve and its branches when exposed through an axillary anterior arm approach.

METHODS

Bilateral upper limbs of 10 fresh cadavers were dissected after dyed latex was injected into the axillary artery.

RESULTS

Via the anterior arm approach, all triceps muscle heads could be dissected and individualized. The radial nerve overlaid the latissimus dorsi tendon, bounded by the axillar artery on its superior surface, then passed around the humerus, together with the lower lateral arm and posterior antebrachial cutaneous nerve, between the lateral and medial heads of the triceps. No triceps motor branch accompanied the radial nerve's trajectory. Over the latissimus dorsi tendon, an antero-inferior bundle, containing all radial nerve branches to the triceps, was consistently observed. In the majority of the dissections, a single branch to the long head and dual innervations for the lateral and medial heads were observed. The triceps long and proximal lateral head branches entered the triceps muscle close to the latissimus dorsi tendon. The second branch to the lateral head stemmed from the triceps lower head motor branch. The triceps medial head was innervated by the upper medial head motor branch, which followed the ulnar nerve to enter the medial head on its anterior surface. The distal branch to the triceps medial head also originated near the distal border of the latissimus dorsi tendon. After a short trajectory, a branch went out that penetrated the medial head on its posterior surface. The triceps lower medial head motor branch ended in the anconeus muscle, after traveling inside the triceps medial head. The lower lateral arm and posterior antebrachial cutaneous nerve followed the radial nerve within the torsion canal. The lower lateral brachial cutaneous nerve innervated the skin over the biceps, while the posterior antebrachial cutaneous nerve innervated the skin over the lateral epicondyle and posterior surface of the forearm. The average numbers of myelinated fibers were 926 in the long and 439 in the upper lateral head and 658 in the upper and 1137 in the lower medial head motor branches.

CONCLUSIONS

The new understanding of radial nerve anatomy delineated in this study should aid surgeons during reconstructive surgery to treat upper-limb paralysis.

Traumatic Partial Posterior Cord Brachial Plexus Injury in a Patient with Aberrant Innervation of the Long Head of the Triceps by the Axillary Nerve: Implications in Nerve Transfer Surgery

Brachial plexus repair forms an unmet need in terms of posttraumatic rehabilitation, especially the young population, wherein the incidence of accidents is high. This leads to decrease in the number of functionally active years after the accident. We encountered an interesting case of posttraumatic posterior cord injury predominantly affecting the shoulder abduction beyond 15°. An electrodiagnostic study showed a complete lack of conduction within the axillary nerve with reduced conduction velocity in the radial nerve. We took the patient up for the long head of the triceps transfer to the anterior division of the axillary nerve transfer. Intraoperatively, we found that the long head branch was originating from the axillary nerve at the point of division. As it could not be used for neurotization, we transferred the medial head branch of the radial nerve to the axillary nerve. The patient started to show electroclinical improvement after 3 months of the surgery. A few similar cases have been published, as a cadaveric finding. We report this case to highlight the possibility and need for a high clinical suspicion and also to provide a possible treatment option, in such aberrant anatomy.

Anatomical study of the masseteric and obturator nerves: Application to face transplant and reanimation procedures

The masseteric nerve (MN) and the anterior branch of the obturator nerve (ON) that innervate the transferred gracilis muscle have proved highly efficient for reanimating paralyzed facial muscles when muscle transfer is required. Previous researchers have published the total axonal load for myelinated fibers in both nerves. However, the real motor axonal load has not been established. We performed the study on 20 MN and 13 ON. The segments of the MN and the ON were embedded in paraffin, sectioned at 10 μm, and stained following a standard immunohistochemical procedure using anti-choline acetyltransferase to visualize the motor fibers. The MN has a higher axonal load than the ON. There were statistically significant differences between the axonal load of the proximal segment of the MN and the ON. These findings confirm that end-to-end anastomoses between the MN and the ON should preferably use the proximal segment. However, MN neurotomy should ideally be performed between the proximal and distal segments, preserving innervation to the deep fascicles. Our results show that the MN is ideal as a donor motor nerve for reinnervating transplanted muscle for dynamic reanimation of the paralyzed face. The neurotomy should ideally be performed between the first and second collateral branches of the MN. Clin. Anat. 32:612-617, 2019. © 2019 Wiley Periodicals, Inc.

Ulnar Nerve Innervation to Triceps: A Cadaveric Study and a Technical Note on Partial Triceps to Biceps Transfer

BACKGROUND

The loss of elbow flexion is a routinely encountered problem in clinical practice. There is no literature on ulnar nerve innervation to triceps in addition to the radial nerve which is dual nerve innervation to triceps in the Indian population. We intend to study the incidence of ulnar nerve innervation to the medial head of triceps in Indian population and also the clinical feasibility of transfer of long and medial head of triceps tendon to biceps around the medial aspect of humerus.

MATERIALS AND METHODS

A cross-sectional study was conducted using 32 fresh-frozen skeletally mature cadavers of Indian origin. The possible contribution of the ulnar nerve to medial head of triceps in addition to the radial nerve was recorded. The arm length, the distance where the ulnar nerve pierces the medial intermuscular septum from medial epicondyle; the distance of the ulnar nerve fascicle from the medial epicondyle was also measured.

RESULTS

The incidence of ulnar nerve innervation to the medial head of triceps was 43.8%. Mean arm length was 29.13 cm. Mean distance where the ulnar nerve pierced the medial intermuscular septum from medial epicondyle was 9.93 cm. Mean distance of the ulnar nerve branch to the triceps from medial epicondyle was 8.01 cm.

CONCLUSION

This study reveals the presence of dual nerve innervation to triceps in 43.8% of the Indian population. The clinical implication would be to look for the possible contribution of the ulnar nerve fascicle to the medial head of triceps, which will help us to include the medial head along with the long head of triceps while performing partial triceps-to-biceps tendon transfer, and the other use would be as a donor fascicle when performing a nerve transfer.

Relationship between the ulnar nerve and the branches of the radial nerve to the medial head of the triceps brachii muscle

One branch of the radial nerve to the medial head of the triceps brachii muscle (MHN) has been described as accompanying or joining the ulnar nerve. Mostly two MHN branches have been reported, with some reports of one; however, the topographical anatomy is not well documented. We dissected 52 upper limbs from adult cadavers and found one, two, and three MHN branches in 9.6%, 80.8%, and 9.6% of cases, respectively. The MHN accompanying the ulnar nerve was always the superior MHN. The relationship between the ulnar nerve and the MHN was classified into four types according to whether the MHN was enveloped along with the ulnar nerve in the connective tissue sheath and whether it was in contact with the ulnar nerve. It contacted the ulnar nerve in 75.0% of cases and accompanied it over a mean distance of 73.6 mm (range 36-116 mm). In all cases in which the connective tissue sheath enveloped the branch of the MHN and the ulnar nerve, removing the sheath confirmed that the MHN branch originated from the radial nerve. The detailed findings and anatomical measurements of the MHN in this study will help in identifying its branches during surgical procedures. Clin. Anat. 00:1-16, 2018. © 2018 Wiley Periodicals, Inc.

Surgical Implications of Innervation Pattern of the Triceps Muscle: A Cadaveric Study

The innervation pattern of triceps is complex and not fully comprehended. Anomalous innervations of triceps have been described by various authors. We have attempted to delineate the nerve supply of the triceps and documented the anomalous innervations of its different heads. The brachial plexus and its major branches (in the region of the axilla and arm) and triceps were dissected in 36 embalmed cadaver upper limbs. Long head received one branch from radial nerve in 31 (86%) specimens. Four (11%) specimens received two branches including one that had dual innervation from the radial and axillary nerves, and one (3%) specimen had exclusive innervation from a branch of the axillary nerve. Medial head received two branches arising from the radial nerve in 34 (94%) specimens. One (3%) specimen received three branches from the radial nerve whereas one (3%) had dual supply from the radial and ulnar nerves. Lateral head received multiple branches exclusively from the radial nerve, ranging from 2 to 5, in all (100%) specimens. Knowledge of the variations in innervation of the triceps would not only help the surgeon to avoid inadvertent injury to any of the nerve branches but also offers new options for nerve and free functional muscle transfers.

Connections between radial and ulnar nerve at high humeral level in cadavers: incidence, topography, and literature review

PURPOSE

Although communications between branches and cords of the brachial plexus have been extensively published, there is a scarcity of reports concerning radial and ulnar nerve (RN-UN) communication in the arm. The current study aims to demonstrate the incidence, topography, and length of communicating branches between RN and UN. Any additional coexisted variations were also recorded.

MATERIALS AND METHODS

Two hundred and sixty-six upper limbs collected from one hundred and thirty-three (81 males and 52 females) Greek cadavers were dissected.

RESULTS

Three out of one hundred and thirty-three cadavers, accounting for an incidence of up to 2.3%, were found to have an atypical communicating branch originating at a high humeral level from RN towards UN. In two cadavers, communicating branches were detected on the left side and in one cadaver bilaterally.

CONCLUSIONS

The study of atypical communications between RN and UN attracts great attention for its clinical importance, mainly in cases of peripheral neuropathies with diagnostic dilemma or upper limb nerve injury producing an otherwise unexpected symptomatology due to the aberrant nerve supply. Familiarity with these variations is crucial in avoiding misdiagnosis and preserving valuable communicating branches, thus achieving an uneventful outcome in cases of upper limb nerve injury repair.